Unit 2 - Innate Immunity & Antibody Structure Flashcards
What are the 5 components in Innate Immunity?
- Physical Barrier
- Phagocytes & Inflammation
- Natural Killer Cells
- Circulating Pattern Recognition Molecules
- Cytokines
What are the stages to an infection?
- Adherence to the epithelium
- Local Infection, penetration of epithelium
- Local infection of Tissues
- Adaptive Immunity
What cells are active when an infection penetrates the epithelium?
antimicrobial proteins
phagocytes destroy invading microorganisms
T cells are sometimes activated
What cells are activated when an infection of the tissues occurs?
Cytokines Phagocytes Natural Killer Cells Macrophages Dendritic Cells migrate to lymph nodes to initiate adaptive immunity
How are phagocytic cells activated?
microorganisms release substances during inflammation that attract phagocytic cells
What are the steps of Phagocytosis?
- Microbe adheres to phagocyte, forming pseudopods
- Phagocytic vesicle (containing the antigen) fuses with a lysosome to become a Phagolysosome
- The microbe in the fused vesicle is killed and digested by lysosomal enzymes.
- Indigestible & residual material is removed by exocytosis
What are TLR’s?
What can the activation of these trigger?
Receptors that recognise bacteria
Triggers the production of pro-inflammatory cytokines which leads to initiation of adaptive immune response
What three things does the Inflammatory response cause?
- Vasodilation- increased blood flow to tissues
- Increased Capillary Permeability- fluid leak into tissues (tissue swelling)
- Influx of white blood cells- migration of phagocytic cells into tissues
What is the Lectin Pathway?
cascade reaction in the complement system, produces complement proteins down the cascade
What is the acute phase response?
What does it cause an increase of?
An innate body defence seen during acute illnesses
Causes an increased production of blood proteins by cytokines
What are acute phase proteins?
A group of proteins produced by the liver that promote inflammation & activate the complement cascade
What is C3? What is its role in the Complement Cascade?
Complement Protein
Converted to C3a & C3b
C3b is deposited on bacterial surface & acts as a marker for recognition by receptors & can also act as an enzyme in the attack of the bacterial membrane
C3a- stimulates inflammatory response
Viruses are detected by the presence of double stranded RNA.
What protein recognises these double strands?
TLR3
Where are antibodies found in the body?
Blood, Secretory fluids (mucus, milk)
Antibodies are only produced by _________
B Lymphocytes
Collectively, a group of antibodies is known as __________
Immunoglobulin (Ig)
What is Avidity?
Avidity- a measure of strength of the interaction of an antibody with an antigen at multiple sights
What are the five isotopes of a heavy chain in an antibody?
IgM, IgG, IgA, IgD and IgE
What are the two types of light chain that could appear in an antibody?
Kappa
Lambda
Which Ig classes are monomers? What about dimers?
Which one is a pentamer?
Monomer- IgG, IgD, IgE & IgA
Dimer- IgA
Pentameter- IgM
What are the three major roles of IgA?
- defence against local infection in respiratory or gastrointestinal tract
- prevents invading organisms from penetrating the epithelium
- antiviral - prevents viruses entering host cells
Large parasites cannot be ingested by phagocytes but when coated in which Ig what happens?
when coated in IgE, eosinophils can attack IgE using Fc receptors
What causes symptoms of hay fever?
Antigen crosslinking of bound IgE links the Fc receptors & triggers degranulation of mast cell- releases anti inflammatory mediators (histamine) and causes hay fever
Hay fever is also known as type ___ ___________
type one hypersensitivity
What are two features of IgM?
- good agglutinator because of pentameric form
- good complement fixing or complement activating antibody
- not good at neutralising toxins
What are the steps in B Cell Activation to create Plasma Cells? (4)
- Cell surface immunoglobulin of B cell binds bacteria and degrades them to produce peptides
- the bacterial peptides are bound via MHC Class II in vesicles & transported to the cell surface
- TH2 recognises the complex and activates the B Cell
- B Cell proliferates & differentiates into antibody secreting plasma cells
What is Linked Recognition?
T Cell dependent antigen responses require the activation of B cells by helper T Cells that respond to the same antigens
Which proteins drive the proliferation and differentiation of the B Cell into antibody secreting plasma cells?
IL-4, IL-5 and IL-6
What class of antibody is the first that’s produced when an antigen arises?
IgM
_____ is produced after repeated challenge to the same antigen
HINT- [class of antibody]
IgG
What is Somatic Mutation?
What are the benefits of it?
a mechanism for introducing mutations into V regions of activated B cells.
Increases antibody affinity after repeated exposure to the same antigen
What is the method of Somatic Mutation?
4
- Mature B Cells travel to the lymph node via the bloodstream and leave via the lymph
- B Cells that encounter antigens form primary foci
- proliferating cells migrate to the primary follicle and form a secondary follicle with a germinal centre
- the germinal centre induces somatic mutation
What is a germinal centre?
a specialised microenvironment that allows B cells to differentiate into antibody secreting plasma cells or memory B cells
What are T- independent antigens role in Somatic Mutation?
the second signal can be delivered by the antigen itself- this activated a large number of B cells known as B-Cell Mitogens
